The most common and most likely answer to this crossword clue is the 3 plus 2 letter word PUT IN
P
U
T
I
N
Buddy explains!
The straight part
We know that "It’s his historic fourth term/submit!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s his historic fourth term/submit! = put in.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PUT IN mean?
PUT IN noun- Restarting play by rolling or throwing the ball into the scrum; the right to do this